Method of preparing vacuum-tubes.



0. E. BUCKLEY.

METHOD OF PREPARING VACUUM- TUBES.

APPLICATION FILED DEC. 30, m5.

1 72,374, Patented July 16, 1918.

UNITED STATES Paras orrron.

OLIVER ELLSWORTH BUCKLEY, OF EAST ORANGE, NEW JERSEY ASSIGNOR TO WESTERNELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. C, A CORPORATION OF NEWYORK.

METHOD OF PREPARING VACUUM-TUBES.

To all whom it may concern:

Beit known that I, OLIVER ELLSWORTH BUCKLEY, a citizen of the UnitedStates, re-- siding at East Orange,in the county of Essex and State ofNew Jersey, have 111- vented certain new and useful Improvements in theMethods of Preparing Vacuum- Tubes, of which the followingis a full,

clear, concise and exact description.

Thisinvention relates to the preparation of vacuum tubes, in particularto thermionic devices having a heated cathode, an anode and an auxiliaryelectrode.

Its object is to provide for heating the anode by vigorous bombardmentof electrons without endangering the. cathode, such bombardment beingdesirable in order to that treatment is to disintegrate the cathodedrive out gases'occluded inthe anode.

This object is accomplished by limiting the current in the tubebyapplying a nega-- tive charge to the auxiliary electrode, and

by then applying a large voltage between anode and cathode by which theenergy of the striking electrons is increased to a value larger thannormal.

In the construction of vacuum tubes in which it is desired to maintain ahigh vacuum, it has been found that unless the electrodes and walls ofthe vessel have been subjected to a vigorous preliminary treatment, thegases occluded by them will slowly leak out with the resultthat thevacuum is soon decreased'and ionization by collision can then takeplace. This preliminary treatment is usually carried out by heating thewalls of the vessel externally and by direct- 3 ing a stream ofelectrons toward the anode.

The present invention insures that the electrons striking the anodeshall do so under the influence of a large voltage and consequently withlarge kinetic energy, while at Specification of Letters Patent. PatentedJ uly 16, 1918, Application filed December 30, 1915. Serial No. 69,418.

the same time this large voltage is not able to draw more thannormalcurrent from the cathode.

In a thermionic device of the type described, if the potential of theauxiliary electrode is made negative with respect to the cathode, alarger voltage between anode and cathode is necessary to produce thesame current from the cathode as would appear in the absence of such avoltage applied to the auxiliary electrode. But the kinetic energy ofthe electrons striking the anode increases with" the increased voltage,and it is therefore possible, by applying a negative potential to theauxiliary electrode,

to increase the vpltage effective in driving electrons to the anode verymuch above the normal value, Whlle maintaining the current at 1ts normalvalue. By th1s process the vigorous bombardment of the anode is may beheated externally. The glass tubing 3 serves to connect the tube with amolecular pump 4 or other suitable means for exhausting it. The liquidair-trap 10 is included in this line of tubing for the usual purpose.The filament 5 is heated by means of alternating current furnished to itthrough the medium of the transformer 8,

whose primary winding is energized by means of the source of alternatlngcurrent,

not shown in the drawing. The voltage between anode and cathode issupplied by means of the direct current generator 9, while theelectromotive force required to maintain the auxiliary electrodenegative with respect to the cathode is obtained from the battery 11,whose negative pole is connected to the auxiliary electrode.

During the. processv of evacuation the pump is operated,-the filamentheated and a discharge started between anode and bardment of the anodeat the increased voltage is contmued until no evidence of gaseousionization in the tube canbe detected.

' release of gas from the anode. In the later As an example of thevoltages employed in one type of tube, it has been found that in theearly part of the process a maximum of about 200 volts'can be maintainedbetween the cathode and the anode. By applying 110 volts between thecathode and the auxiliary electrode, making the latter nega-. tive, amaximum of 500 volts or more may be obtained with consequent more rapidstagesof exhaust a potential difference of 750 volts or more may bemaintained by the use of the negative auxiliary electrode, while if thatelectrode were disconnected it would not be more than 550 volts. Afurther advantage of this method is that during the process ofbombardment the negative auxiliary'electrode attracts to itself thegreater part of the positive ions released by the electron discharge,and thereby prevents the bombardment of the cathode by these ions, whichbombardment, as is well known, tends to disintegrate the cathode.

ode, an anode and an auxiliary electrode,

which method consists in evacuating said tube and before said evacuationis completed in performing the following steps, 2'. e. in maintaining anelectron discharge between said cathode and anode and in applyingbetween said auxiliary electrode and said cathode a voltage which shalllimit the current to a given value while permitting a large voltagebetween anode and cathode whereby the energy of the electrons strikingthe anode shall be large.

2. The method of preliminary treatn'lent of a vacuum tube containing aheated cathode, an anode and an auxiliary electrode,

which method consists in evacuating said tube and before said evacuationis completed in performing the following steps, 2'. e. in maintainingthe auxiliary electrode at a negative potential with respect to theoathode and in applying between anode and cathode a voltage sufficientto maintain a desired current in the tube.

lrl witness whereof, I hereunto subscribe my name this 28th day ofDecember, A. D.-, 1915.

OLIVER ELLSWORTH BUGKLEY

